1. Field of the Invention
This invention relates to a wedge socket and wedge connector for coupling a wire rope to an object. More specifically, this invention relates to an improved wedge socket and wedge that prevents the wedge from disengaging the wedge socket.
2. Description of the Invention Background
When lifting, moving or pulling objects by use of a crane, hoist or other powered machinery, for example on a construction site, a wire rope is commonly used to transfer movement from the power source to the object to be moved. One end of the wire rope is typically attached to a power source, such as a vehicle, or to a mechanism such as a spool which is connected to the power source. Wire rope as commonly used on a crane, for instance, runs from the spool where it is wound, up an arm and over a pulley, where it hangs down to be used for various lifting, moving, pulling or other construction purposes.
At the free end of the wire rope, it is necessary to attach in some manner the wire rope to the object to be lifted. One mechanism used to attach the wire rope to the object is a wedge socket assembly. The object is then attached to the wedge socket assembly, either directly via a jaw and pin formed integrally into the wedge socket assembly or via a block, hook or other mechanism attached to the jaw and pin of the wedge socket assembly. Common applications for a wedge socket assembly include high dynamic uses such as pile drivers, drag lines, clamshell operations, and the like, and more static uses such as mining applications, elevator applications, and the like.
The wedge socket assembly typically comprises a wedge socket and a wedge which fits into the wedge socket. The wedge socket comprises a hollow elongated basket of substantially rectangular cross-section which is open at both ends. The inside of the basket of the wedge socket is tapered from one opening to the other, so that one opening is smaller than the other. The wedge is similarly shaped as the interior of the basket of the wedge socket --i.e. it is tapered, is of substantially rectangular cross-section, and is substantially the same size as the interior of the basket. The wedge typically will have a groove which runs around its longest circumference. The groove is typically of similar diameter as the wire rope with which it is to be used.
The wire rope is attached to the wedge socket assembly by running it through the hollow basket of the wedge socket from the smaller opening to the larger opening, positioning the wire rope in the groove around the circumference of the wedge, and running the wire rope back through the hollow basket of the wedge socket from the larger opening to the smaller opening. The wedge with the wire rope around it is then inserted into the basket of the wedge socket, trapping the wire rope between the edge of the wedge and the interior sides of the basket. The taper of the wedge and the taper of the inside of the basket of the wedge socket combine so that when tension is put on the wire rope, the wedge is pulled by the wire rope tightly into the basket, retaining the wedge and wire rope firmly in place. A forged wire rope clip is then attached to the tail, or dead end, of the wire rope.
A pair of jaws are cast integral to the wedge socket on the side of the wedge socket away from the side where the wire rope enters. A pin is inserted through a pair of coaxial holes formed transversely through the jaws of the wedge socket and is held in place with a cotter pin. The object to be moved or lifted, such as a clamshell bucket, can then be connected directly to the wedge socket by passing the pin through a hole in a tab formed in the object designed for that purpose. Alternately, a block, hook or some other holding means can be connected to the wedge socket by the pin, and an object can be connected to the holding means.
During a typical operation, the wedge and wire rope are forced into the wedge socket with enough force that the wedge will remain in place. However, a reverse force on the wedge socket assembly could generate slack in the wire rope running around the wedge and the wedge can be jarred loose from its engaged position in the wedge socket.
In certain high dynamic applications, such as pile driving, clamshell operations, or the like, the object attached to the wire rope stops suddenly, such as, for instance, in pile driving, when the driver impacts the pile. Upon impact, the wedge socket assembly stops suddenly as well. However, the wire rope wants to continue moving, and its momentum will redistribute itself because it can no longer move forward. The wire rope, being fairly stiff, will build up a substantial column of force before buckling. This column of force will travel linearly in the direction of movement until the wire rope buckles. The column of force is applied directly into and against the wedge socket assembly and can unseat, or punch out, the wedge from within the basket of the wedge socket.
Similarly, in other high dynamic applications, such as drag line operations and the like, the power source may stop suddenly, thus stopping the wire rope equally as suddenly. In this situation, the object being moved wants to keep moving, and thus the object will push the wedge socket assembly directly into the wire rope. Again, the wire rope will create a column of resistance before buckling, which may cause the wedge to punch out from the wedge socket.
If the wedge punches out of the basket of the wedge socket, the wire rope may jump or fall out of the groove around the circumference of the wedge. The wedge itself may then become lodged between the ears or between the basket and the ears of the wedge socket, or cocked at an angle in the basket, with the wire rope pinned between an edge of the wedge and a portion of the basket. When further weight or tension is applied to the wire rope, the wedge and socket can cut or weaken the pinned rope.
One method of preventing the wedge from becoming disengaged from the wedge socket is to use a forged wire rope clip to attach the wire rope tail to the portion of the wire rope under tension, or live end. This method has the disadvantage that with every impact the wire rope will slide minutely around the wedge to reseat itself, which will cause the forces to distribute themselves such that all of the weight of the object being lifted may be placed on the forged wire rope clip, creating an eccentric load. The efficiency of the eccentric load is only about sixty percent.
It is thus seen that there is a need for a wedge socket which overcomes these shortcomings.